This invention relates generally to plows and more particularly to an improvement in snow plows and similar devices for cleaning snow and other debris from roadways and similar surfaces.
The invention is particularly applicable to a snow plow apparatus and construction, whereby an improved moldboard is provided and will be described with particular reference thereto. However, the invention may have broader applications and could be used, in theory, for plows for other applications such as agricultural purposes and the like.
A plow of the type used to remove snow from a roadway must include a blade which rolls the snow upwardly and then moves it transversely across the face of the blade. To accomplish this, the plow includes a moldboard having a curvilinear configuration which terminates in a lower plowing edge or a scraper blade. The scraper blade usually extends in a forward direction and, in effect, digs into the snow and forces the snow onto the curvilinear moldboard. The contour of the moldboard imports a rolling action to the upwardly moving snow and forces the snow transversely across the face of the moldboard and to the side of the plow.
Over the years many different moldboard configurations of various curvilinear shapes have been experiment with to arrive at a shape which would insure smooth rolling and transverse movement of wet and powdery snow across the moldboard face. A curvilinear configuration, essentially arcuate in shape and extending in only one planar direction has proven an acceptable, widely used geometrical configuration for the moldboard.
A typical snow plow construction is to roll a mild steel carbon plate, typically of about 1/8", into an arcuate shape to form the moldboard. The framework, typically constructed from structural angle members, is then welded to the rear side of the moldboard to support and prevent the moldboard from fracturing when being hit by rock and other debris from the roadway while also providing the structure for the attachments necessary to operate the plow. Typical examples of such construction may be found by reference to U.S. Pat. No. 3,432,947 to Peitl and 3,465,456 to Meyer assigned to the current assignee and incorporated herein by reference.
From a consideration of plow weidht, a steel moldboard is undesirable. It obviously places greater force requirements on the vehicle to which it is attached, and perhaps more importantly requires heavier plow attachments and larger lifting systems than what otherwise may be possible.
From an efficiency consideration, a number of attempts have been made to improve the efficiency of the steel moldboard in plows of the aforesaid type so as to better enhance the rolling motion and transverse movement of the snow across the face of the moldboard. Many of the approaches fundamentally involve a lowering of the coefficient of friction of the surface of the moldboard. For example, wax has long been used by snow plow operators on the moldboard. Moldboards have also been permanently coated with various substances. However, such coating eventually fail when struck by rocks, stones and other debris from the roadway which impact the moldboard under significant forces.
A number of various materials having extremely low coefficients of friction exist in the art. In particular, ultra high molecular weight polyethylenes have been developed and applied in industrial application where sliding contact is encountered as for example as liners for chutes and bunkers, as wear strips, slide plates, bearings and bushings. Until now, considerations relating to the mechanical properties of such materials have ruled out the suitability of such materials for use as a moldboard in a snow plow application.
More recently, on the basis of weight and cost considerations alone, various types of other plastics have been used as moldboards in snow plows. The plastic is preformed into the desired curvilinear shape and applied flush against the frame where it is drilled and fastened in place in the same manner that the steel moldboard is conventionally applied to the frame. Depending upon the properties of the plastic and its durability, plastic moldboards have met with limited success.